Method of forming oven liners



July 28, 1953 Filed Sept. 21, 1949 J. W. INGRAHAM ET'AL METHOD .OF FORMING OVEN LINERS 2 Shets-Sheet 1 5 viii wmuzsssg INVENTORSI- JA MES W. INGRAHAM 'ALFONS BARNSTEINER ATTORN EY J. w. INGRAHAM EI'AL- 2,646,762

mom 0? FORMING OVEN LINERS July 28, 1953 2 Sheets-Sheet 2 Filed Sept. 21, 1949 l l l l M W E SMN R H. Y mMT E NGS.. N ENN R W m llw z s in M MP L A ll W 5 a m m7 W w WM fclosed by a door; 7 throate'd front flange member, a rear wall mem- Patented July 28, 1953 V UNITED- STATES PATENT OFFICE,

METHOD OF FORMING OVEN LINERS James W. Ingraham and Alfons Barnsteiner, Mansfield, Ohio, assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 21, 1949, Serial No. 116,901

1 Claim. 1 This invention relates to ovens and more particularly to a method of making a fabricated sheet metal oven liner. In a present construction of a welded sheet vmetal oven liner for an: electric range, the oven ."liner is fabricated of three separately formed pieces. The liner is generally rectangular in ,eross-section and encloses a substantially cubical baking compartment closed on all sides except the" front. The front opening is adapted to be The liner includes an openber and'an intermediate body member, assembled into one rigid unit by spot-welding at numerous points;

' "Handling of the front member prior to assem- Tlbly may distortfthe flange ofthe front "member and impair its 'tru'eness Also, during the weldingoperation, the liner issubjected to considerable hat, causing expansion of the metal and producingunpredictable thermal stresses which ma'ynwarp the fiange of the front member. Although the flange has ,a U-shaped cross-section which is highly'resistant to normal cooking heat stresses, 'the'highfjlocalized heat stresses which oc'curduring the welding operationmay impair the trueness of the .flange which is so desired for a good seal "between the oven door and the lineriiangef To correct the warpage incurred in handling and welding,- the welded "oven liner is placed in a set of dies and the flange is subjected to aflnal truing or sizing operation which is intended to restorethe flange to its original trueness. However, since the flange is formed with such arigid cross-section initially,

vide-an eifective method of"truingthe front 'flange of an oven liner after the same has been warped or distorted during its manufacture, such as may be caused by the thermal stresses induced during the welding process and in handling.

These'and other objectsare efiected by the invention-as'willbe apparent from the following description and claim taken in connection with the accompanying "drawings, forming a part of this application, in which:

Fig. is a vertical section of a finished oven liner assembled in a range;

, Fig. 2 is a partial section-of the oven liner,- in

perspective, showing an .intermediatestag e I of fabrication;

Fig. 3 is aview similar to Fig. 2, showing the completed liner; and

- Figs. 4 to 7, inclusive,-are schematic-sectional .v views showing the oven liner in the various stages of fabrication, in accordance with our invention.

Referring to Fig. 1, a sheet metal oven liner, generally designated I0, is shown having an intermediate body member l2 closed at its rear end by a wall member l4 and having an open-throated front member 16. As well known in the art, the intermediate member is made of sheet metal and is bent to form a tubular structure of rectangular cross-section having a top wall l8, a bottom wall and two side walls 22 (only one shown). The rear wall member [4 is drawn to the shape of a shallow pan and has a vertical wall 24, the marginal portion of which is rounded and extended to provide an outwardly offset peripheral portion 26 which externally embraces the intermediate member to form a rabbet joint therewith. The joint is preferably secured as by spot-welding at a plurality of spots 28. The front member I6 has a rectangular opening defined by a continuous wall 30 having its rear marginal portion extended to provide an outwardly offset peripheral portion 32, similar to the offset portion 26, which externally embraces the front end of the intermediate member to form a rabbet joint therewith. This joint is also secured by spot-welding at a plurality-of spots 28. The front member has an outwardly disposed flange 34, which with the wall 30, is U-shaped or channel-shaped.

As shown in Fig. 1, the oven liner is disposed within a range body including a front outer panel 36 and a rear outer panel 38. The front panel has an opening defined by an inwardly displaced flange 40 adapted to abut the liner flange 34. An inner sheet member 42 is horizontally disposed below the oven liner [0 and is joined to the front and rear panels 36 and 38, respectively. The sheet member 42 carries a channel member 44 support the rear portion of the liner.

" The position of the liner is determined by I abutment of the liner flange 34 against the front panel flange 40, the liner being maintained in such position by two fastening plates 46 attached to the liner and two hook bolts 45 which have hook portions engaging in openings in the plates 46 and which'are adjustably secured to the rear outer panel 33. Also, as well known in the art, the oven may be insulated against excessive heat loss during its operation by a layer of. heat insulating'material, such as spun glass 49.

According to our invention, the intermediate body member 12 may be formed in any desired manner, as well understood "in the'art. However, as shown in Fig. 4, the front member [6 andtherear member l4 may be initially integral and may be formed of fiat sheet metal stock as well understood in the art. The outer marginal portion of the sheet is unformed and is left in its original planar state, providing a preliminary flange 5 I. The flange 5| is substantially flat and is, therefore, relativelyweal; in crosssection in a direction substantially normal t o-its face. The flange thus lends itself to ready alteration by dies to ultimately provide the-flange 34 of the front member, as will be subsequently explained.

As shown schematically in Fig. 4, after the pan is drawn to shape, it is subjectedto"theaction of a restriking and trimming die having a lower member 52 adapted to support the pan and an upper member 54 adapted to restrike and trim the untamed pan portion. omy the right half of the die members 52 and 54 is shown, for clarity, since the left half of the die members is the same. Theiupper member 54 has a shear- "ingpdition 55 and a Striking ahdhbldihg 1501- tion 58. \ivith respect tothe member 54 and is biased The portion 58 is movable vertically d wnwarmy 'therefr'or'n'by spring meanest. To

perform the restriking and trimming operation,

the pan 50 is inserted withinthe die member 52 while the upper die member 54 is in retracted portio'ri'158 is to flatten the surface of the flange,

j while the efiect of the trimming portion at is to true" edge of the flange. The flange 5] has a' rounded connecting portion 66 of'relatively 'la'rge radius, for a reason which will later be s l fii q:

After the above'rest'riking and trimming operation completed, the pan is severed 'on line X--X and subjected to theaction ofrollersinot shown) to provide '(as shown in: Fig. 53 a prelimi'nary front liner memher "6 8 "and the 7 rear member, I 4 the peripheral 'ofiset portions j iii-ad ztir sp i e l.we. i w schematically therhethod of assemblingthe front a e mem e s] t 't e, .ii t rmd ate int e l2. The front and rear members are positioned with their offset pardons 3'2 and '26, respectiveiy,

in lapping engagement and forming ra'bb'et joints with the intermediate 'memher. 'They'are then rigidly tions' 28 I I I I a parrot 'op'po'sedelectrodes T2 connetited to u ite'dfby spot-welding at numerous posiusing spot-wadingequipments-onionsing action is imparted to the metal, particularly at the rounded portion 90, during this reforming operation, which eliminates any irregularities or I war'page Whi'ch*may have been incurred by the fiange during any of .the preceding operations or handling.

After the die inerhbers 1E and 80 come together,

the die member- -82 will move downwardly, as

shown in Fig, 7, to complete its stroke. The outer marum portio'n' ofthe flange will be bent downwardly to complete the flange 34 as it apa power supply, to form a unitary oven'l'in'er "structur'el' l in "its intermediate stage of fabrication as also 'shownin greatly eiiagg'erated 'proportion in Fi 2.

he liner "structure"!!! is then inserted in 'a'set ofio'rming dieswhitzh' as shown in Figs. 6 and 7, f comprise a lower annulardie member 1 6 and an hpper iorming die member 18 adapted to'act-on "theflange 5 *an'd the rounded portio'n'6 6 and to reformthem tothe final flange 34. Thefup'per "'die'member has a'male member 80 and 'a "female member 82 biased vertically by spring means 84,

' in Fig. 6, and movable withTr'es'pect to each other." "on the downward snake, die inerhbrto strikes the flange '5 andthe rounded portion 65, compressing 'them "against the lower die rriember as shown inFig. 6. The die'm'emberslfi aridBllhave active portions8 6- and 88,

respectively, which are different in shape from therounded flang e portion 66111 that they have a smaller radius of curvature. Thus, the rounded pears in the completed liner I0. Although not shown, the lower die member '16 may be of the well-kno'wn gate type which permits insertion of the work piece from thes'id'e instead "of-the top. Also, as shown in Figs, fiand 7, 'the lower 'fdi'e member may becut awayat portion 92 to afford relief and clearance for theoffs'etportlibn '32'when the oven liner is withdrawn from the die.

It will now be seen that we 'have'provided an ovehuner having a front fla'n'ge' which is g'i'ea'tly improved in trueness at no iaddedfcost. The final I sizing operation in conventional usagehasbeen baking results will'be obtained. I

While we have shown our invention in buthne form, it will be obvious to thoseskilled in -the art that it is not so limited, but is suscelitibl'e'ibf "various changes and-"modifications without departing from the spiritthereof.

What we claim is: I I II The method of forming an oven liner having an open side comprising the steps of forming a member having a tubularwall-encompassingthe oven adjacent said open side, a preliminary-flange extending outwardly from @the tubular wall suba-stantially in the plane of the open side and aconnecting portion of relatively large radius joi-ning the tubular wall and the flange, Joining other wall portions of the liner to said-member by welding, and thereafter reforming said connecting portion to a smaller radius of curvature-and bendingback the outer marginal portion of-said preliminary flange to provide a channel or U- shaped portion of the liner around-said open-side.

JAMES INGRAHAM. i 'ALFONS BARNSTEHNER.

References Cited in the file-of this p'a'tent UNITED STATESPATENTS Number Name Date I 1,888,374 Cromwell Nov. 22 E332 2,253,499 Rllthbei '-+Aug-. 26, 1941 2,378,982 Chesney June 26,- 1945 'FOREIGN PATENTS Number Country Date 50,243 Austria Oct. 19, ;1911 235,979 Great Britain July 2, 1925 

